4-Bromo-2-hydroxybenzoic acid

4-Bromo-2-hydroxybenzoic acid is a solid at normal temperature and pressure. It is stable at normal temperature and decomposes into phenol and carbon dioxide after rapid heating. It has some acidic properties.

Under nitrogen atmosphere, add copper (II) bromide (8.8 g, 39.4 mmol, 1.2 equivalents), acetonitrile (50 ml), and 4-aminosalicylic acid (5.1 g, 49.5 mmol) to the vacuum-dried reaction flask, 1.5 equivalent). The reaction mixture was cooled to 0°C, and 2-hydroxy-4-bromobenzoic acid precursor (5.0 g, 32.6 mmol, 1.0 equiv) was added portion-wise. Additional acetonitrile (25 mL) was added to the mixture and stirred at 0 °C for 2 h. The organic extracts were combined and washed with 20% aqueous hydrochloric acid, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The residue was dissolved in diethyl ether, and the resulting solution was extracted with 15% sodium hydroxide aqueous solution. The aqueous solution was washed with diethyl ether, acidified to pH 1 with 6N hydrochloric acid aqueous solution, and the mixture was extracted with diethyl ether. The combined organic extracts were washed with brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The residue was treated with chloroform, and the precipitate collected by filtration was 4-Bromo-2-hydroxybenzoic acid.